1. Field of the Invention
This invention generally relaters to storage technology and, more particularly, to method and apparatus for migrating thin provisioning volumes between storage systems. In addition, this invention relates to unification of a storage resource pool.
2. Description of the Related Art
To reduce storage costs, management costs and power consumption, thin provisioning capability in storage systems has been implemented. With thin provisioning, a storage system provides virtual volumes as storage area to store data for host computers. In the virtual volumes, the storage system allocates and assigns physical data storage areas only to target locations of a write access command received from host computers. Because not all virtual storage locations are associated with physical storage location, the total amount of used physical area in pool can be smaller than total amount of virtual area shown to the host computers. To achieve this capability, the storage system divides storage area (e.g. storage area in HDD or flash memory) into plurality of fixed-length areas called chunks or pages, and manages mapping between chunks and logical segments in the virtual volumes.
For example, U.S. Pat. No. 7,162,600, incorporated herein by reference, discloses techniques for implementing thin provisioning in a storage system and for utilizing external storage. Specifically, methods for migration between normal (not thin provisioning) volumes and thin provisioning volumes are disclosed.
However, because the thin provisioning is independently implemented in each storage system, efficient migration of thin provisioning volumes between multiple storage systems is not easily achieved. That is, migration of thin provisioning volumes requires transferring the entire storage capacity of the virtual volumes between storage systems even if the virtual volumes store only a small amount of actual data. Specifically, the conventional technology does not provide a method for achieving efficient migration of thin provisioning volumes when the chunk length is deferent between the storage systems.
Migration of volumes between storage systems may be required when data stored in the volumes is moved from old storage system to new storage system for repurposing/reuse of the old storage system or when storage environment is reconstructed in order to achieve centralized management on one storage system with virtualization of external storage (e.g. unifying storage resource pool).
Therefore, what is needed is a method and apparatus to achieve efficient migration of thin provisioning volumes between storage systems and to unify the storage resource pool.